37signals usually do things right, and customer service is not an exception. In December customers of their real-time chat application, Campfire, experienced downtimes and overall unstable behavior. Not being able to access web applications sucks, and especially if you're a paying customer and your daily business life depends on it. But shit happens, right? This can happen to the best (customers of Apple's MobileMe weren't that happy in the initial shaky stages). What's dead important and actually good act in your favor is how you handle the crisis. In the linked article Jason Fried tells us a little bit about how they communicated with their customers during the downtime. They used real words for this real problem, not corporate talk. They wrote a blog post explaining exactly what had happened and what measures they took to make sure it wouldn't happen again. As the title of the article says, they turned this negative event to further show their customers how much they care.
And we've discovered that the more honest we are, the better our customers feel. They just want to know what's going on and what happened. They want to be informed.